Bonding of metal carbonyl deposits



1 Patented July 12, 1949 BONDING F METAL CARBONYL DEPOSITS Albert 0. Fink, Dayton, Ohio, assignor to The Commonwealth Engineering Company of Ohio, Dayton, Ohio, a corporation of Ohio No Drawing. Application April 20, 1946,

. Serial No. 665,318 g 1 This invention deals with a method of plating metals, and in particular with a method based on the decomposition of gaseous metal carbonyls.

In coatings obtained from metal carbonyls, the disadvantage heretofore has frequently been encountered of the coating not sufliciently adhering to the base metal. Moreover, the metal coating would become blistered if the object so coated was raised to elevated temperatures, for example in a heat treatment process.

2 Claims. (Cl. 11'l65) It is an object'of this invention to provide a blistering.

It is still another object of this invention to provide a method of producing metal coatings which may be subjected to a heat-treatment process without thereby impairing the adherence of the coating.

These and other objects are accomplished by depositing the metal coating in two steps and inserting a heat-treatment step therebetween.

In the first coating step, only a very thin porous film is applied to the base metal by decomposing gaseous metal carbonyl. A layer of 0.00001" to 0.00025", preferably of 0.00005" to 0.00015", was found most satisfactory; however, the invention is not restricted to this range. After this first layer has been applied, the coated article is heated. By this heating step, the gas which has been adsorbed at the surface of the base metal is driven off and escapes through the thin metal layer due to its porosity, and the thin metal coating is thus more strongly bonded to the base metal. For the the case of plating copper with nickel, a temperature of from 800 to 900 F. was found most advantageous. Of course, the higher'the heating temperature used, the shorter heating time required. Heating to temperatures of from 500 to 1200 F. for a period of from 2 to 30 minutes was found to be satisfactory. A metal coating of the desired thickness is thereafter applied to this 'pre.. treated base metal, again b decomposing metal carbonyl. The product thus obtained is characterized by an excellent bond of the coating to the base metal and by a very uniform and smooth surface structure.

After the deposition of the coating layer proper a second heat treating step may be applied; however, this is not obligatory. Sometimes by such an after-treatment by exposure to high temperatures the ductility of the coating layer is increased. I r

For the intermedIat heat treatment it isnecessary that it be carried out in a non-oxidizing, but preferably in a reducing, atmosphere. Nitrogen, carbon monoxide. carbon dioxide, hydrogen, natural gas, commercial brazing furnace gas or a mixture of such or other gases known in the art are suitable for this purpose. "*In the following, the process is described by way of example as applied to the coating of copper with nickel.

Example A copper plate was first mechanically cleaned by sanding. Thereafter the copper metal was heated to approximately 375 F. in an atmosphere containing approximately 1.4 per cent by volume of nickel carbonyl and diluted with carbon dioxide gas. The rate of gas flow was approximately 4 l. per minute at a temperature of 78 Rand mm. Hg. The copper was exposed to this atmosphere for about 2 minutes after which time a film of 0.00007 thickness had formed on the copper base. Thereafter the metal was heated in an atmosphere of natural gas to a temperature of about 800 F. for approximately 15 minutes. After these preliminary steps the coating proper was performed by subjectin the metal to the same conditions and gases as in the preliminary film-forming step. This second step was carried out for about 15 minutes when a coating of 0.0004" had formed.

In order to increase the ductility of the coating, I subjected the metal to an additional heating step. This step consisted in heating for 15 minutes to a temperature of from 800 to 900 F. in an atmosphere of natural gas.

The process of my invention is applicable for plating with all metals which form gaseous carbonyls; thus, plating with chromium, iron, tungsten, cobalt, molybdenum and other metals may be successfully carried out by the method described. The heat treatment after the application of a thin porous metal film eliminates the gases adsorbed on the surface of the base metal, and the surface activity is then immediately utilized for strongly bonding this metal film,

Thus, the coatings obtained by the process of my invention are uniform in structure, free from blisters and well-adhering to the base metal. Heat treatment does not impair the firm bond between the coating and the base metal.

It will beunderstoodthatthisinventionis not to be restrictedto the examples given in the speciflcation, but that it is e to various mod-,

iflcations and changes which come within the spirit of the disclosureand'the scope of the ap-' pended claims.

I claim:

1. ma process of depositing metal on a copperbase material by the decomposition of metal carbonyl, the steps of exposing the copper base to a carbon dioxide'atmosphere containing 1.4% by volume of a metal carbonyl from the group consisting of nickel, chromium, iron, tungsten, cobalt, and molybdenum for aperiod of time of approximately two minutes while said copper base material is heated to approximately 375' F., said gas having a rate of flow of approximately 4 1. per minute at a temperature of 78 F. and 125 mm. Hg; 0! then heating said copper base with said metal fllmthereon to approximately 800 F. for about 15 minutes in an atmosphere of natural gas and then exposing said coated article to the same metal carbonyl containing gas as the under coat until the coating of the desired thickness has been obtained.

2. In a process for depositing nickel on a copper base material by the decomposition of metal carbonyl the step of exposing it to a carbon dima amen 4 containing percent by volume of nickel carbonyl-for a periodic! tim'eot approximately 2 minutes while said copper base ms terial' is heated to approximately 375 F. said s REFERENCES CITED The following references are of record in file of this patentf UNITED s'ra'rms PATENTS the Number Name Date 1,752,239 Ferrantl Mar. 25, 1930 2,063,596 Feller Dec. 8, 1936 2,332,309 Drummond .........1 Oct, 19, 1943 FOREIGN PATENTS Number Country 7 a Date 487,854 Great Britain Sept. 22, 193B 

